1. Field of the Invention
The present invention relates to a photosensitive silane-coupling agent, a method of modifying a surface and a method of forming a pattern using such photosensitive silane coupling agent, and a method of fabricating a device.
2. Description of the Related Art
Recently, in the fields of various electronic devices which require microfabrication, such as semiconductor devices, there has been ever increasing demands for increased density and integration of the devices. In the step of fabricating a semiconductor device, it is the photolithography process that plays an important part in forming the fine circuit pattern.
Most current photolithography processes are carried out by reduced projection exposure. However, the resolution of reduced projection exposure is limited by the light diffraction limit, which is about one-third the wavelength of the light source. Thus, attempts have been made to achieve shorter wavelengths using techniques such as employing an excimer laser as the exposure light source, whereby microfabrication at about the 100 nm level is now possible.
Thus, although photolithography continues to have improving fineness, many problems needing to be resolved have arisen, such as the increased size of the equipment resulting from shortening the wavelength of the light source, as well as development of lenses for such wavelength region, equipment costs and costs of the corresponding lenses.
Further, devices have recently been proposed which require a high-density dot array pattern. Examples thereof include a single-electron device (Japanese Patent Application Laid-Open No. 2001-168317), patterned media (Japanese Patent Application Laid-Open No. 2005-190624), a chemical sensor (Japanese Patent Application Laid-Open No. 2003-268592), a quantum dot laser element (Japanese Patent Application Laid-Open No. H10-012968), and a photonic crystal optical device (Japanese Patent Application Laid-Open No. H11-218627). However, because these devices require even greater high-precision microfabrication techniques than those for semiconductor devices, mass production has been difficult with conventional photolithography techniques.
On the other hand, as a low-cost and simple method for forming a micropattern taking the place of lithography techniques, methods have been reported which cause the microparticles to arrange in a self-organizing manner.
Further, in recent years methods have also been proposed for forming a micropattern by forming a chemically reactive group in a pattern on a substrate surface using an energy beam, and then utilizing the interaction between the chemically reactive group and the microparticles. Specific examples are disclosed in Polymer Preprints, Japan, Japanese Ed., Vol. 53, 4196 (2004) and Japanese Patent Application Laid-Open No. 2003-168606. These examples are techniques which fuse lithography and self-organization. In the present invention such techniques will be referred to as “build-up lithography”.
In Polymer Preprints, Japan, Japanese Ed., Vol. 53, 4196 (2004), it is disclosed to expose a monomolecular film of a photosensitive silane coupling agent to a light, and then adhere microparticles to the exposed portion.
Specifically, it is disclosed to irradiate UV rays onto a photosensitive silane coupling agent having a carboxyl group which is protected by a nitrobenzyl group to thereby generate a carboxyl group on the irradiated portion, and to dip the resultant object in an aqueous solution of fluorescent microparticles for selectively adhering fluorescent microparticles to the exposed portion.
Polymer Preprints, Japan, Japanese Ed., Vol. 53, 4196 (2004) also discloses the results of examples in which a monomolecular film of a photosensitive silane coupling agent having an unsaturated alkyl group was irradiated with X-rays in a pattern to excite the unsaturated bonds of the exposed portion, whereby bonds were formed with the organic film of the surface of the metal microparticles.
The photosensitive silane coupling agent used in Polymer Preprints, Japan, Japanese Ed., Vol. 53, 4196 (2004), which has a carboxyl group protected by a nitrobenzyl group, generates a nitrosobenzaldehyde as a byproduct upon exposure. To remove this byproduct, a rinsing step is necessary. However, in mass production of a device, a smaller number of steps is preferable from the perspective of costs.
Further, in Japanese Patent Application Laid-Open No. 2003-168606, there is the problem of a high rate of defects due to the microparticles not properly adhering to the energy beam irradiation portion. This is because the excited state of the unsaturated bond group is easily deactivated to the ground state.